In today's digital world, an enormous amount of content is available. Thus, whether the content is stored on a user device such as a personal computer or available to users via the World Wide Web, keyword searching has long been the conventional means for identifying content items of interest to a user. For example, Internet search engines such as the Yahoo! Internet search engine and the Google Internet search engine are both keyword search engines. As another example, personal computers typically include software applications that enable their users to perform keyword searches of content stored on the local hard drives of the personal computers. However, such keyword searching processes are blunt instruments. Users need more powerful and intuitive means to search content.